linux-kernel - [PATCH] Check maxlen on strnlen

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Message-ID: <4E601794.6080202@gmail.com>
Date:	Fri, 02 Sep 2011 09:39:00 +1000
From:	Ryan Mallon <rmallon@...il.com>
To:	Mark Salter <msalter@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>
CC:	linux-fsdevel@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] Check maxlen on strnlen_user usage

strnlen_user returns the length of the string including the nul 
terminator. In the case where maxlen is reached strnlen_user returns 
maxlen + 1. Most callsites already check for this condition. Fix the 
call to strnlen_user in fs/exec.c to check for the maxlen case.

Signed-off-by: Ryan Mallon <rmallon@...il.com>
---

diff --git a/fs/exec.c b/fs/exec.c
index 25dcbe5..e19588c 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -481,7 +481,7 @@ static int copy_strings(int argc, struct user_arg_ptr argv,
  			goto out;

  		len = strnlen_user(str, MAX_ARG_STRLEN);
-		if (!len)
+		if (!len || len>  MAX_ARG_STRLEN)
  			goto out;

  		ret = -E2BIG;

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